Skip to content
Skip to content

Learn

How do you calculate a plywood price escalation clause using the PPI?

Compare the current value of BLS series WPU083 (Plywood) to its value at contract signing, turn that into a ratio, and apply the ratio to the plywood-affected line items. A usable clause also names an averaging window, a publication-lag rule, and a cap.

The mechanism

A plywood escalation clause indexes the plywood-affected portion to a published series instead of fixing it at signing. The benchmark is the BLS producer price index for Plywood, series WPU083.

Plywood is a real input cost in sheathing and subfloors, concrete formwork, and crating and packaging work. Its price can move more over a contract term than a fixed-price contingency is built to absorb, so indexing the plywood-affected portion moves that risk onto the published index instead of onto one party.

What's specific to plywood

Plywood swings with housing starts as sharply as lumber does, and sheathing grade and sanded finish grade can move in opposite directions within the same quarter. The clause should name the grade, not just "plywood".

The calculation, step by step

  1. Base index value. The index value at the base period, usually the month of contract signing or bid submission.
  2. Current index value. The index value at the adjustment date, usually the month of delivery or invoicing.
  3. Ratio. Current value divided by base value.
  4. Adjustment. Apply the ratio to the plywood-affected portion, not necessarily the whole contract.

Take a clause with a $140,000 plywood-affected scope, a base index of 260.0, and a current index of 292.0. The ratio is 1.12, a 12% increase, so $16,800 is added to that scope.

Where clauses go wrong

The most common mistake is not naming a series code. "The plywood index" is not a series. BLS publishes more than one plywood-related series, so name the exact code, WPU083, in the contract text.

Clauses also skip the averaging window. A single month's value swings more than a 3-month rolling average, so the clause should say which one applies. Publication lag gets left out the same way: BLS releases data on a delay and revises early figures, so the clause should say whether the preliminary or final value governs.

The last common gap is no cap or floor. With no cap, an index spike passes through in full, which can make a large adjustment commercially unworkable.

Related reading

How do you calculate a steel price escalation clause using the PPI?

A steel PPI escalation clause compares a current-period Producer Price Index value for a named steel series to the value at contract signing (the base period), turns that into a ratio, then applies the ratio to the contract price or affected line items. Clauses typically define the exact BLS series code, an averaging window, a publication lag, and a cap limiting the maximum adjustment.

Read more →

See this calculated automatically

Escalake tracks the index, applies the formula, and gives both sides a number they can confirm, no spreadsheet required.